Experimental Investigation Of Mode I/II/III Fracture Behaviors Of Additively Manufactured Polymer

Abstract

Material extrusion (ME) additive manufacturing (AM) technique gained importance in fabricating polymer engineering parts. It is necessary to characterize the fracture behavior of fabricated polymers before using them in applications. Fracture is observed in three modes of loading called mode I, II, and III; and all three should be investigated to provide a comprehensive insight into fracture properties. Studies about the fracture behavior of ME-fabricated polymers usually ignore investigating all three fracture modes. To address this gap, this study aims to investigate the fracture behavior in three modes (modes I, II, III) for the polylactic acid (PLA) polymer, fabricated by ME. For mode I and II, single-edge notch bending (SENB) specimens were fabricated and tested in a four-point bending test. Linear elastic fracture mechanics (LEFM) were used to extract the Mode I/II fracture properties. For mode III, a new device was designed and manufactured to facilitate imposing Mode III loading with the help of a universal tensile testing machine. Relevant equations were utilized to compute the Mode III fracture toughness. Moreover, the corresponding fracture energies were calculated through the formulations of LEFM. Dog-bone specimens were also fabricated to extract Young’s modulus through tensile test and digital image correlation.